Physicists Study Colliding Atoms With a Laser Tracker
Leica's LTD500
Hundreds of physicists from
around the world come to Brookhaven National Laboratory
to study what the universe might have looked like in the
first few moments after its creation. The laboratory in
Long Island, New York, is a world-class scientific research
facility that began operation of its Relativistic Heavy
Ion Collider in 2000, following 10 years of development
and construction. RHIC drives two intersecting beams of
gold ions head-on in a subatomic collision that forms heat
and new particles. What physicists learn from these collisions
may help them understand more about why the physical world
works the way it does, from the smallest subatomic particles
to the largest stars.
Using Leica's LTD500 laser tracker system to ensure accurate
alignment of the beams to within 0.050 mm (50 µm),
Brookhaven physicists are able to align the intersecting
beams of gold ions to ensure head-on collisions. The 3-D
measurement system is a robotic laser interferometer incorporated
into Leica's Axyz software, used for large-scale metrology.
The interferometer is the standard calibration instrument
for distance measurement, measuring distance by counting
wavelengths of light in a differential scheme. The LTD emits
a laser beam, and a reflector located on the object returns
the beam along a parallel path back into the sensor head.
The returned signal is used to calculate the distance to
the reflector. The tracker head continuously traces the
movement of a prism and reports coordinates.
RHIC, the world's newest and biggest particle accelerator
for nuclear physics, comprises several accelerators working
together to produce collisions of heavy ions--atoms which
have their outer layer of electrons removed. The RHIC collides
two beams of gold ions as they travel in opposing orbits
at 99.95-percent the speed of light. At such a speed, the
gold ions appear to flatten and then collide. The collision
is transformed into intense heat and new particles.
Physicists sift through these particles' energy and type
for information to help them understand more about the physical
world. The RHIC produces collisions that occur thousands
of times per second. Each one acts as a microscopic pressure
cooker, producing temperatures nearly 40,000 times that
of the sun.
Leica incorporated the laser tracker and the multihead
theodolite modules into the Axyz system to database the
results of the 3-D points generated in space. The system
is capable of taking 1,000 measurements per second and has
an overall accuracy of 0.001 in.
Physicists work in 3-D when surveying these experiments
to examine the layout of magnets and detectors, which is
structured and formal. The nature of object location can
take place in presurvey mode, in which an object's internal
mechanical or magnetic features are measured and related
to external fiducials for layout, or in post-survey mode,
in which an object is located after the beam operation.
The successful implementation of the Leica LTD500 allows
Brookhaven physicists to bring the RHIC up to full collision
energy of 100 billion electron volts (GeV) per nucleon.
Until then, the RHIC was colliding ions at a maximum energy
of 65 GeV. With these higher temperatures, the chances are
increased of colliding particles reaching "boiling
point," the temperature at which quarks and gluons
can escape from inside protons and neutrons. This added
energy produces more than 100 times the data than did collisions
during the first year of the RHIC's operation.
Leica's LTD500
- Internal automatic function control
- 3-D determination
- High-precision angular encoders for a diameter of 70
m
- Measuring rate of up to 1,000 points per second
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